MOT for Freelander - 2 wheel brake tester ? (AGAIN !)

Interesting theory - not sure I agree with it, because I've never heard of a Freelander's tranmission going bang at a testing station - which if it was a primary contributing reason for failure it would be likely to occur there regularly.

 

Sheesh and gawd damn
I DID lol
No wonder Kiwi fruits are higher priced than Marijuana...................................

4 (four) wheel Drive....

tum te tum te tum ....

 

I think it may well be a contributing factor to failure - not necessarily at the time - I think excessive loading leads to weakening of - or initial damage to components or - more likely - instigation of the primary damage to the components - this then progresses... the damage is done - the failure is the result of the unit(S) further down the line.
Fatigue failures are not (usually) instantaneous) - rather they are progressive.
Hypothesis but hey .......

 

I normally remove my VCU for the MOT as I like to see the brake performance and if there is any bias to one side or another. I refit the props after the test is done, knowing that the brakes are A 1.

 

Here is a link to a fairly good site that explains the need for using a 4 wheel rolling road.

http://workshop-manuals.com/landrover/freelander-b/general_information/rolling_road_testing/

 

Here in france when the tester inputs the vehicle data at the start of the test the computer flags up that it needs the extra rollers put down for the brake test. This is just a heavy frame with a pair of rollers that is laid on the floor behind the standard brake tester so the rear wheels sit on it and can spin freely as the fronts are tested. It then needs picked up and dragged to the front of the tester so the front wheels sit on it as the rears are tested.

Last test, the guy obviously couldnt be bothered so he just tried to test as a normal 2wd car. When the rollers start turning the front wheels, they encounter abnormal resistance as the VCU tries to turn the rear wheels so he couldnt get a baseline reading of whether the brakes were binding or not. Further insistance trying to get a reading meant that the rear wheels started to turn and pushed the car off the rollers.
No damage done....its only for a few seconds at a time, and no different to having a pair of wheels stuck in sticky mud. The more you insisit with the rollers, the harder the VCU locks up and either the rear wheels will slip on the garage floor or will push the car forwards out of the tester. I guess if your IRD was on the point of failure anyway this could provoke it to break, but a healthy one should be able to take this kind of abuse for a reasonable period of time.

 

To put it bluntly, I've no sodding idea why they lock the front and rear rollers and test just one axel when they've done them with the wheels left to rotate. But that's what they always do. It's all over within 2 minutes, and no damage has ever been done.
The Freelander doesn't go back in for its test til November, but I shall do my best to remember and ask.
As for the bit about 2wd, I had verbal diarrhoea and couldn't stop
Mike

 

Hi Dave, you raise an interesting and somewhat valid point - that being that in most circumstances the transmission should be quite able to deal with the issues and make the test - basically - not possible - due to the vehicle forcing itself of the rollers.. However, the testers who are not aware of the issues tend to do the following (as they normally do on a 2WD vehicle - they place - what they consider to be the 'driven' wheels on the 2WD rollers and then apply the hand brake if they consider the unit to be an FWD unit - as many do with the FL. Now you are forcing against the handbrake locking the rear wheels. My FL handbrake - after much trials and tribulations - is absolutely superb ! - anyone that locks that and then applies drive to the front wheels is applying a huge load on the transmission - without the handbrake - this would not necessarily be the case.
Some great points are being highlighted here - thanks all for a good discussion.
Joe

 

But if the rear wheels are locked with the handbrake then when the rollers try to turn the fronts the VCU will tighten and the front wheels will lock up too, making a brake reading impossible.
IMO tyres will slip on the rollers before damage is likely to be done.

 

Ah, I knew it must be in there somewhere ! - from RAVE -

Brake testing on a two wheel brake test dyno - you must REMOVE rear prop-shaft.

The MOT brake test rollers are a two wheel dynamometer

That is direct from Land Rover



Had to be documented somewhere...............

 

And same for the non abs


Joe.

 

Ooops, sorry, I posted virtually identical info - apologies

Good to have it clarified once and for all though !